Hybrid type telephony system

ABSTRACT

The hybrid type telephony system capable of establishing a connection between conventional type telephone sets contained in an exchange unit and LAN type telephone sets contained in an IP network, the system comprising: a gateway circuit connected between the exchange unit and the IP network and performing voice data format conversion, and a central control unit connected to the LAN of the IP network for establishing a communication path to the exchange unit via a control bus, controlling switching of IP packets of the IP network, managing IP address information of the LAN type telephone sets and the gateway circuit via the LAN, and controlling connection between the LAN type telephone sets and connection between the LAN type telephone sets and the gateway circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hybrid type telephony system and inparticular, to a hybrid type telephony system capable of providing asingle service to both of a conventional type telephone set contained ina time-division switch and a LAN type telephone set contained a LAN.

2. Description of the Related Art

With reference to FIG. 4, explanation will be given on a conventionaltelephony system including a private branch exchange unit and a LAN typetelephone system.

In FIG. 4, a private branch exchange unit 150 is based on atime-division switch 100. The time division switch 100 has a functionfor switching 64-Kbps time division data. A central control unit 101 hasa function for controlling the entire exchange unit 150. A subscribercircuit 102 and a subscriber circuit 103 are interface circuits ofconventional type telephone sets having a function of voice interfaceand a function to control conventional type telephone sets. A trunkcircuit 104 has an interface function for interfacing with otherexchange units and apparatuses. A gateway 107 has a function for dataconversion between time division data handled by a private branchexchange unit and voice packets handled by a LAN type telephone system.Conventional type telephone sets 105 and 106 may be ordinary analogtelephone sets or multi-function telephone sets for a private branchexchange unit. Moreover, a LAN switch 108 has a function for switchingpackets on the LAN. A LAN 109 and a LAN 110 are LAN networks. A LAN typetelephone set 111, a LAN type telephone set 112, and a LAN typetelephone set 113 are LAN type telephone sets connected contained in theLAN. A server 114 has a function for a call connection between the LANtype telephone sets 111, 112, 113 and the gateway 107 and other service.

When constructing a telephone service system by using a private branchexchange unit and a LAN type telephone system, the exchange unit 150 isconnected to the LAN type telephone system via the gateway 107. In thiscase, a line having a 64-Kbps speed is used for connection between thetrunk circuit 104 of the private branch exchange unit 150 and thegateway 107 while a LAN is used for connection from the gateway 107 tothe LAN switch 108.

For example, when calling from the conventional type telephone set 105to the LAN type telephone set 111, upon off-hook of a receiver of theconventional type telephone set 105, the subscriber circuit 102connected to the conventional type telephone set detects the off-hookand reports it to the central control unit 101.

The central control unit 101 performs a call processing such as sendinga dial tone to the conventional type telephone set 105 and receives aselection signal as a telephone number of the destination from theconventional type telephone set 105. In this case, the selection signalis a combination of an access number for catching the trunk 104 and atelephone number of the LAN type telephone set 111 on the LAN typetelephone system. For example, when it is assumed that the access numberfor catching the trunk 104 is “8” and the telephone number of the LANtype telephone set 111 is “111”, the selection signal will be “8111”.

The central control unit 101, upon recognition of that the selectionsignal from the conventional type telephone set 105 is “8111”,establishes a communication path between the subscriber circuit 102 andthe trunk circuit 104 through the time division switch 100 and transmitsa selection signal “111” from the trunk 104 to the gateway 107.

With this, the gateway 107 recognizes that the call from the trunk 10 isa call to the LAN type telephone set 111 and performs a call processingto the server 114 including inquire of the IP address of the LAN typetelephone set 111, so that a voice information packet is transmitted andreceived between the gateway 107 and the LAN type telephone set 111.This enables communication between the conventional type telephone set105 and the LAN type telephone set 111.

Moreover, Japanese Patent Publication 10-308777 discloses a voiceexchange system of a LAN terminal in which a LAN subscriber circuit iscontained in a line interface block of an electronic exchange unit towhich a terminal such as a LAN type telephone set is connected via aLAN. In this voice exchange system, voice data from a LAN terminalalways passes through the LAN subscriber circuit and the main switch ofthe electronic exchange unit. Accordingly, even a communication betweentwo LAN type telephone sets on the LAN is performed via a path formed bya first LAN type telephone set, a first LAN subscriber circuit, the mainswitch, a second LAN subscriber circuit, and a second LAN typetelephone. In this case, voice compression is performed as follows.Firstly, voice data is compressed in the first LAN type telephone set 1and transmitted via the LAN to the first LAN subscriber circuit, wherethe voice data is restored. After this, the voice data is transmittedfrom the first LAN subscriber circuit to the main switch and thencompressed in the second LAN subscriber circuit. The compressed voicedata is restored in the second LAN type telephone set.

In the conventional telephony system using a private branch exchangeunit and a LAN type telephone system, the private branch exchange unitand the LAN type telephone system operate as completely differentsystems which are connected via a gateway. Accordingly, it is impossibleto provide a unitary service. For example, for a communication between aconventional type telephone set contained in a private branch exchangeunit and a LAN type telephone set it is necessary to input an accessnumber (such as 8) indicating a route via a gateway and a telephonenumber (such as 111) in a destination system.

Moreover, in the aforementioned voice exchange system, voice data issignificantly deteriorated because compression-restore is repeatedtwice. Moreover, compression and restore require not little time.Furthermore, when transmitting a voice packet using a LAN, the voicepacket transmission is delayed with a delay time fluctuating dependingon the packet. To cope with this, a plurality of voice packets isaccumulated for a predetermined period of time before restoring thevoice packets, so as to absorb the fluctuation. However, while repeatingthe compression-restore process, the time for absorbing the fluctuationsbecomes great resulting in a great delay time, greatly affecting thevoice quality.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a hybridtype telephony system integrating an exchange unit and a LAN typetelephone system so as to prove a common service to all the telephonesets.

Another object of the present invention is to provide a hybrid typetelephony system integrating a private branch exchange unit and a LANtype telephone system capable of maintaining a voice quality andproviding a unitary service.

The hybrid telephony system according to the present invention ischaracterized in that conventional type telephone sets contained in atime division switch of an exchange unit such as a private branchexchange unit and LAN type telephone sets contained in a LAN arecontained in an integrated apparatus, enabling to provide an integratedservice for the conventional telephone sets contained in the timedivision switch and the LAN type telephone sets contained in the LANwithout distinguishing them from each other. More specifically, in thehybrid telephony system integrating the private branch exchange unit andthe LAN type telephone system, traffic between the conventional typetelephone sets contained in the exchange unit or traffic between the LANtype telephone sets contained in the LAN type telephone system areconnected by the time division switch and the IP switch, respectively.As for traffic between the conventional type telephone sets contained inthe exchange unit and the LAN type telephone sets contained in the LANtype telephone system is connected by performing voice data formatconversion via a gateway circuit between the time division switch andthe IP network (such as an IP switch).

The hybrid type telephony system according to the present invention iscapable of establishing a connection between conventional type telephonesets contained in an exchange unit and LAN type telephone sets containedin an IP network, the system comprising: a gateway circuit connectedbetween the exchange unit and the IP network and performing voice dataformat conversion, and a central control unit connected to the LAN ofthe IP network for establishing a communication path to the exchangeunit via a control bus, controlling switching of IP packets of the IPnetwork, managing IP address information of the LAN type telephone setsand the gateway circuit via the LAN, and controlling connection betweenthe LAN type telephone sets and connection between the LAN typetelephone sets and the gateway circuit.

More specifically, the hybrid telephony system includes: a time divisionswitch for switching between subscriber circuits and a time divisionmulti-path of the gateway and switching PCM signals input/output from/tothe subscriber circuits and the gateway circuit; an IP switch forswitching IP packets flowing on the LAN (see 30 to 34 in FIG. 1)according to destination information contained in the header of each ofthe IP packets; and a central control unit for controlling the timedivision switch, the IP switch, the subscriber circuits, and the gatewaycircuit as well as packet routing between the LAN type telephone setsand the gateway circuit by communication with the LAN type telephonesets using the LAN. The gateway circuit makes a PCM data from the timedivision switch into an IP packet and transmits the packet to the LAN(34). Upon reception of an IP packet from the LAN (34), the gatewaycircuit transmits a voice data in the IP packet to the time divisionswitch (12). Here, data passing between the time division switch and thegateway circuit is performed using PCM data (in case voice data iscompressed for passing on the LAN, the gateway circuit has the functionfor voice compressing/restoring). Moreover, the subscriber circuitscontain conventional type telephone sets (25, 26), transmits/receives avoice signal between the conventional type telephone sets and the timedivision switch, monitors the states of the conventional type telephonesets, reports states such as call and release to the central controlunit, and upon reception an instruction from the central control unit,causes ringing. The LAN type telephone sets (20 to 22) has a LANinterface and has a function for transmitting and receiving voice dataand call processing information using IP packets.

The conventional type telephone sets transmit and received voice signalsto/from the subscriber circuits and is switched by the time divisionswitch for communication with a destination. The LAN (30 to 34) areconnected to the IP switch for transmitting and receiving IP packets.The time division network (40) is a time division network of 64-Kbpsbasis and connected to another exchange unit or the like. The WAN (41)is connected via a network router (45) for transmitting and receivingpackets to be transmitted/received to/from a remote LAN. The router (45)has a routing function for routing packets to be transmitted/receivedto/from a remote location using the WAN (41). The call control, servicecontrol, and the maintenance/operation service are integrated in asingle central control unit, thereby enabling to provide an integratedservice.

[Function]

The hybrid system including a conventional exchange unit (such as aprivate branch unit) system using the time division switch as a kerneland a LAN type telephone system constituted by LAN type telephone setsfunctions as follows. For a call between conventional type telephonesets contained in the conventional exchange unit and a call between LANtype telephone sets contained in the LAN type telephone system, aconnection is made on the time division switch and the LAN switch/LAN,respectively. As for traffic between a conventional telephone setcontained in the conventional exchange unit and a LAN type telephoneset, connection is established by performing a voice data formatconversion via the gateway circuit. The central control unit performingcontrol of the time division switch and the LAN switch is contained in aLAN connected to the LAN switch and transmits/receives call informationand destination IP address via the LAN, and controls the traffic betweenthe conventional telephone sets contained in the conventional exchangeunit and the LAN type telephone sets via the gateway circuit and thetime division switch communication path.

By arranging both of the conventional telephone sets 25, 26 contained inthe time division switch and the LAN type telephone sets 20, 21, 22contained in LAN in the hybrid telephony system, it is possible toprovide an integrated service without distinguishing between theconventional type telephone sets 25, 26 and the LAN type telephone sets20, 21, 22.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a hybrid type telephony system according to a firstembodiment of the present invention.

FIG. 2 shows a hybrid type telephony system according to a secondembodiment of the present invention.

FIG. 3 shows a hybrid type telephony system according to a thirdembodiment of the present invention.

FIG. 4 shows a conventional telephony system using a private branchexchange unit and a LAN type telephone system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Description of Configuration]

FIG. 1 shows a hybrid type telephony system according to a firstembodiment of the present invention. The hybrid type telephony system 1according to the first embodiment includes: a central control unit 10; atime division switch 12 having a gateway circuit 14 and subscribercircuits 15 and 16; an IP switch 13; and a control bus 17 used by thecentral control unit 10 for controlling the time division switch 12, theIP switch 13, the subscriber circuits 15 and 16, and the gateway 14.Moreover, the hybrid type telephony system 1 includes LAN's 33 and 34connected to the IP switch 13. The central control unit 10 is containedin the LAN 33 while the gateway 14 is contained in the LAN 34.

The central control unit 10 controls the entire hybrid type telephonysystem 1. Using the control bus 17, the central control unit 10 controlsthe time division switch 12, the IP switch 13, the subscriber circuits15 and 16, and the gateway circuit 14. Moreover, using the LAN, thecentral control unit 10 performs communication with LAN type telephonesets 20, 21, 22 and controls packet routing between the LAN typetelephone sets 20, 21, 22 and the gateway circuit.

The time division switch 12 performs switching between time divisionmulti-paths of the subscriber circuits 15, 16 and the gateway 14 as wellas switching of PCM and other signals input/output from/to thesubscriber circuits 15, 16, and the gateway circuit 14.

The IP switch 13 switches packets according to destination informationcontained in the header of each IP packet flowing to the LAN's 30, 31,32, 33, 34.

The gateway 14 has a function to makes PCM data from the time divisionswitch 12 into an IP packet and transmit it to the LAN 34 and a functionto transmit to the time division switch 12 a voice data contained in theIP packet received from the LAN 34. Here, data is passed between thetime division switch 12 and the gateway 14 using a 64-Kbps PCM data.Since voice data is compressed for transmission and reception on theLAN, the gateway 14 also has the function for voice compression andrestore.

The subscriber circuits 15 and 16 contain conventional type telephonesets 25 and 26 and passes a voice signal between the conventional typetelephone sets 25 and 26 and the time division switch 12, monitors astate of the conventional type telephone sets, reports states such ascall and release to the central control unit 10, and causes to theconventional type telephone sets 25, 26 to ring.

The LAN type telephone sets 20, 21, 22 have a LAN interface function anda function for transmitting and receiving voice data and call processinformation using an IP packet.

The conventional type telephone sets 25 and 26 transmit and receive avoice signal to/from the subscriber circuits 15 and 16, respectively andcan communicate with a destination switched by the time division switch12.

The LAN's 30, 31, 32, 33, 34 are connected to the IP switch 13 and cantransmit and receive IP packets.

The time division network 40 is a 64-Kbps based time division networkwhich is connected to another exchange unit and the like.

A WAN 41 is a network for transmitting and receiving packets to betransmitted to/from a remote LAN and is connected via a router 45.

The router 45 has a routing function for routing a packet to betransmitted/received to/from a remote location using the WAN 41.

Since the gateway unit 14 is well know to those skilled in the art anddoes not constitute the main portion of the present invention, itsdetails are omitted here.

It should be noted that while the aforementioned embodiment has beenexplained using the conventional type telephone sets 25 and 26 asterminals to be contained in the time division switch 12, it is alsopossible to use a multi-function telephone used in a exchange unit, PHS(personal handy phone system), ISDN (integrated services digitalnetwork), and the like, including an image terminal or data terminal.

Moreover, while explanation has been given on the LAN type telephonesets 20, 21, 22 as the terminals to be contained on the LAN, it is alsopossible to use other apparatuses such as a personal computer having avoice interface.

While the embodiment has been explained using the gateway 14 having afunction for compressing voice data to be made into a packet, whether tocompress voice data or not can be selected as is desired.

[Description of Operation]

Next, explanation will be given on the operation of the hybrid typetelephony system of the first embodiment shown in FIG. 1. Operation forconnection between conventional type telephone sets, between LAN typetelephone sets, and between a conventional type telephone set and a LANtype telephone set will be explained as a connection between theconventional type telephone set 25 and the conventional type telephoneset 26, a connection between the LAN type telephone set 20 and the LANtype telephone set 21, and a connection between the LAN type telephoneset 20 and the conventional type telephone set 25, in this order.

(1) Calling from the Conventional Type Telephone Set 25 to theConventional Type Telephone Set 26

When a receiver of the conventional type telephone set 25 is hooked off,the subscriber circuit 15 containing the conventional type telephone set25 detects the off-hook and reports it to the central control unit 10.The central control unit 10 performs a call processing by transmitting adial tone to the conventional type telephone set 25 and causing tooperate a ringer of the conventional type telephone set 26 as thedestination using a selection signal which is a telephone number of thedestination from the conventional type telephone set 25. When theconventional type telephone set 26 responds to this, the central controlunit 10 establishes a communication path of the time division switch 12,thus completing the call processing.

(2) Calling from the LAN Type Telephone Set 20 to the LAN Type TelephoneSet 21

When an off-hook occurs in the LAN type telephone set 20, a dial tonecan be heard from a receiver of the LAN type telephone set 20. In thisstate, when the selection number of the destination LAN type telephoneset is input, the LAN type telephone set 20 transmits a packet for acall processing to the central control unit 10.

Here, the IP address of the central control unit 10 is set in each ofthe LAN type telephone sets in advance, and an IP address of thedestination LAN type telephone set can be identified by inquiring thecentral control unit 10 upon call. Moreover, the LAN type telephone set20 is contained in the LAN 30 and the central control unit 10 iscontained in the LAN 33. Accordingly, the IP packet from the LAN typetelephone set 20 is switched to the LAN 33 by the IP switch 13 to reachthe central control unit 10.

Upon call from the LAN type telephone set 20, if the destination LANtype telephone set 21 is in an idle state, the central control unit 10reports a response wait to the LAN type telephone set 20 and the LANtype telephone set 20 transmits a ring back tone to the receiver.Moreover, the central control unit 10 reports an incoming call to theLAN type telephone set 21 to cause the LAN type telephone set 21 toring. After this, when the LAN type telephone set 21 is hooked off, theLAN type telephone set 21 reports an incoming response to the centralcontrol unit 10. The central control unit 10 reports the IP address ofthe LAN type telephone set 20 to the LAN type telephone set 21 and theIP address of the LAN type telephone set 21 to the LAN type telephoneset 20. Upon reception of the IP addresses, the LAN type telephone sets20 and 21 can communicate with each other by transmitting voice packets.

In case of communication between the LAN type telephone set 20 and theLAN type telephone set 21, since they are contained in the same LAN 30,IP packets passed directly between them. However, in case ofcommunication between the LAN type telephone set 20 contained in the LAN30 and the LAN type telephone set 22 contained in the LAN 31 forexample, IP packets are switched by the IP switch 13 and they are passedvia the IP switch.

(3) Calling from the LAN Type Telephone Set 20 to the Conventional TypeTelephone Set 25

When the LAN type telephone set 20 is hooked off, a dial tone can beheard from the receiver of the LAN type telephone set 20. In this state,when the selection signal of the destination conventional type telephoneset is input, the LAN type telephone set 20 transmits a call processingpacket to the central control unit 10.

If the conventional type telephone set 25 is in the idle state, thecentral control unit 10 instructs the subscriber circuit 15 containingthe conventional telephone set 25 to ring and a call ring can be heardfrom the receiver of the conventional telephone set 25. Simultaneouslywith this, the central control unit 10 reports to the LAN type telephoneset 20 that the destination is being called and a ring back tone can beheard from the LAN type telephone set 20. When the conventionaltelephone set 25 answers by off-hook, the subscriber circuit 15containing the conventional type telephone set 25 reports the responseto the central control unit 10. Upon reception of the report of theresponse from the subscriber circuit 15, the central control unit 10reports the response to the LAN type telephone set 20 and controls thetime division switch to establish a communication path between thesubscriber circuit 15 and the gateway circuit 14. The central controlunit 10 reports the IP address of the gateway circuit 14 to the LAN typetelephone set 20 and the IP address of the LAN type telephone set 20 tothe gateway circuit 14.

The LAN type telephone set 20 and the gateway circuit 14 transmits voicepackets to the IP addresses of the gateway circuit 14 and the LAN typetelephone set 20, respectively, thus passing packets on the IP. Byperforming this together with the aforementioned communication pathestablishment by the time division switch 12, communication can beperformed between the LAN type telephone set 20 and the conventionaltype telephone set 25.

Thus, by establishing the communication path of the time division switch12 and transmitting the destination IP addresses to the LAN typetelephone set and the gateway circuit 14, the central control unit 10performs control enabling any communication in the hybrid type telephonysystem, thereby enabling to constitute a single-management systemaccording to the present embodiment and to provide an integrated servicebetween a conventional type telephone set contained in the time divisionswitch 12 and a LAN type telephone set.

[Other Embodiments]

While the present invention has been described using an example of anetwork having a LAN and a LAN switch, the network system may be anypacket network.

FIG. 2 shows a second embodiment of the present invention applied to anIP network. In this embodiment, it is possible to constitute an IPnetwork in which routing control is performed by a hub or the like,thereby eliminating need of packet switching control by the centralprocessing unit 17. Moreover, the IP network may employ, for example, anATM or a frame relay.

Moreover, the aforementioned embodiments of the telephony service may berealized, for example, as follows. A single extension representationnumber is assigned for a group consisting of a plurality of conventionaltype telephone sets and LAN type telephone sets. For a call from one ofthe telephone sets contained in the group or from a telephone setoutside, the central control unit performs an incoming control for allthe conventional type telephone sets and the LAN type telephone sets inthe group so that all the telephone sets in the group receive theincoming signal and any of the conventional type telephone sets and anyof the LAN type telephone sets can answer. Such a telephony system canbe provided by the present invention.

Moreover, another example of a unitary service for both of theconventional type telephone sets and the LAN type telephone sets isrealized as follows. Since the central control unit can perform theentire management, when a call is made from a conventional typetelephone set to a LAN type telephone set having a display function suchas an LCD, it is possible to display on the LCD the telephone number ofthe conventional type telephone set which has made the call. In case acall is made to a conventional type telephone set having a displayfunction such as an LCD, it is possible to display the telephone numberof the calling telephone set.

Furthermore, with the configuration for the entire management by thecentral control unit, it is possible to employ a maintenance-managementconfiguration for setting extension telephone numbers and the like andperforming maintenance via single interface. FIG. 3 shows a systemcapable of providing such a service. A maintenance/management terminalis provided of a single interface on the central control unit bus forperforming various settings, maintenance, and management, so that thecentral control unit can set control data and monitor control.

FIG. 3 shows a configuration for realizing such maintenance/managementby providing a maintenance terminal in the central control unit. Sincethe conventional exchange unit system and the LAN type telephone systemare operated as a unitary block by the central control unit, datasetting and maintenance can easily be performed with a single interface.Moreover, telephone numbers of conventional type telephone and LAN typetelephone sets can be assigned without limit from the maintenanceterminal.

It should be noted that the central control unit has been described assingle central control unit physically but it can also be realized by aplurality of central control units for dispersing the load or for otherreasons.

As is clear from the aforementioned, the present invention can providethe following effects.

The first effect is that a conventional type telephone set contained ina time division switch or the like and a LAN type telephone setconnected to a LAN can be contained in single system, thereby enablingto provide an integrated telephony service between the conventional typetelephone set and the LAN type telephone set. This enables aconventional type telephone set to get the same service as the LAN typetelephone system.

For example, the control form in the central control unit can be set asfollows.

(a) A plurality of conventional type telephone sets and LAN typetelephone sets are unified into a single group of predetermined size andone extension representation number is assigned for the group. When acall is made to the extension representation number, all the telephonesets in the group receive the incoming signal, so that any of theconventional type telephone sets or the LAN type telephone sets cananswer. Such a telephony service is enabled.

(b) For example, when a call is made from a conventional type telephoneset to a LAN type telephone set having a display function such as LCD,it is possible to display the telephone number of the callingconventional type telephone set. In case a conventional telephone sethas the display function such as an LCD, the telephone number of thecalling telephone set can be displayed on the LCD. Thus, variousservices of the conventional exchange unit (private branch exchangeunit) can be provided for both of the conventional type telephone setsand the LAN type telephone sets without distinguishing them from eachother.

The second effect is that the conventional exchange unit (such as aprivate branch exchange unit) and the LAN type telephone system areoperated as a unitary block, data setting and maintenance can beperformed with a single interface.

The third effect is that since the conventional exchange unit (such as aprivate branch exchange unit) and the LAN type telephone system areoperated as a unitary block, for example, there is no need ofdistinguishing the exchange system and the LAN type telephone systemfrom each other. Telephone numbers can be assigned without anyparticular limit.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristic thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

The entire disclosure of Japanese Patent Application No. 2000-044364(Filed on Feb. 22, 2000) including specification, claims, drawings andsummary are incorporated herein by reference in its entirety.

1. A hybrid type telephony system capable of establishing a connectionbetween conventional type telephone sets contained in an exchange unitand LAN type telephone sets contained in an IP network, the systemcomprising: a gateway circuit connected between the exchange unit andthe IP network and performing voice data format conversion, a centralcontrol unit connected to a LAN of the IP network for establishing acommunication path to the exchange unit via a control bus, controllingswitching of IP packets of the IP network, managing IP addressinformation of the LAN type telephone sets and the gateway circuit viathe LAN, and controlling connection between the LAN type telephone setsand connection between the LAN type telephone sets and the gatewaycircuit, and wherein the control bus forms a communications path forenabling the central control unit to control a time-division switch forthe conventional type telephone sets and an IP switch for the LAN typetelephone sets.
 2. A hybrid type telephony system capable ofestablishing a connection between conventional type telephone setscontained in a private branch exchange unit and LAN type telephone setscontained in an IP network, the system comprising: a gateway circuitconnected between the private branch exchange unit and the IP switch andperforming voice data format conversion, a central control unitconnected to a LAN of the IP switch for establishing a communicationpath to the private branch exchange unit via a control bus, controllingswitching of IP packets of the IP network, managing IP addressinformation of the LAN type telephone sets and the gateway circuit viathe LAN, and controlling connection between the LAN type telephone setsand connection between the LAN type telephone sets and the gatewaycircuit, and wherein the control bus forms a communications path forenabling the central control unit to control a time-division switch forthe conventional type telephone sets and an IP switch for the LAN typetelephone sets.
 3. The hybrid telephony system as claimed in claim 1,wherein the LAN type telephone sets have IP address information of thecentral control unit, upon a call to one of the LAN type telephone setsfrom another of the LAN type telephone sets, the another of the LAN typetelephone sets transmits a call requesting packet to the central controlunit via the LAN according to the IP address information of the centralcontrol unit, inquires the central control unit about a destination IPaddress, and fetches the destination IP address to establishcommunication.
 4. The hybrid telephony system as claimed in claim 2,wherein the LAN type telephone sets have IP address information of thecentral control unit, upon a call to one of the LAN type telephone setsfrom another of the LAN type telephone sets, the another of the LAN typetelephone sets transmits a call requesting packet to the central controlunit via the LAN according to the IP address information of the centralcontrol unit, inquires the central control unit about a destination IPaddress, and fetches the destination IP address to establishcommunication.
 5. The hybrid telephony system as claimed in claim 3,wherein upon a connection between one of the LAN type telephone sets andone of the conventional type telephone sets, the central control unitreports the IP address of the gateway circuit to the one of the LAN typetelephone sets and the IP address of the one of the LAN type telephonesets to the gateway circuit, so as to establish a communication pathbetween the one of the conventional type telephone sets and the gatewaycircuit.
 6. The hybrid telephony system as claimed in claim 4, whereinupon a connection between one of the LAN type telephone sets and one ofthe conventional type telephone sets, the central control unit reportsthe IP address of the gateway circuit to the one of the LAN typetelephone sets and the IP address of the one of the LAN type telephonesets to the gateway circuit, so as to establish a communication pathbetween the one of the conventional type telephone set sets and thegateway circuit.
 7. The hybrid telephony system as claimed in claim 1,wherein the central control unit assigns a single extensionrepresentation telephone number for the plurality of conventional typetelephone sets and the plurality of LAN type telephone sets as a singlegroup and, upon a call from one of the conventional telephone sets orthe LAN type telephone sets using the extension representation telephonenumber, performs a call-incoming processing to all the telephone sets inthe group.
 8. The hybrid telephony system as claimed in claim 2, whereinthe central control unit assigns a single extension representationtelephone number for the plurality of conventional type telephone setsand the plurality of LAN type telephone sets as a single group and, upona call from one of the conventional telephone sets or the LAN typetelephone sets using the extension representation telephone number,performs a call-incoming processing to all the telephone sets in thegroup.
 9. The hybrid telephony system as claimed in claim 3, wherein thecentral control unit assigns a single extension representation telephonenumber for the plurality of conventional type telephone sets and theplurality of LAN type telephone sets as a single group and, upon a callfrom one of the conventional telephone sets or the LAN type telephonesets using the extension representation telephone number, performs acall-incoming processing to all the telephone sets in the group.
 10. Thehybrid telephony system as claimed in claim 4, wherein the centralcontrol unit assigns a single extension representation telephone numberfor the plurality of conventional type telephone sets and the pluralityof LAN type telephone sets as a single group and, upon a call from oneof the conventional telephone sets or the LAN type telephone sets usingthe extension representation telephone number, performs a call-incomingprocessing to all the telephone sets in the group.
 11. The hybridtelephony system as claimed in claim 5, wherein the central control unitassigns a single extension representation telephone number for theplurality of conventional type telephone sets and the plurality of LANtype telephone sets as a single group and, upon a call from the one ofthe conventional telephone sets or the one of the LAN type telephonesets using the extension representation telephone number, performs acall-incoming processing to all the telephone sets in the group.
 12. Thehybrid telephony system as claimed in claim 6, wherein the centralcontrol unit assigns a single extension representation telephone numberfor the plurality of conventional type telephone sets and the pluralityof LAN type telephone sets as a single group and, upon a call from theone of the conventional telephone sets or the one of the LAN typetelephone sets using the extension representation telephone number,performs a call-incoming processing to all the telephone sets in thegroup.
 13. The hybrid telephony system as claimed in claim 3, whereinthe IP address of the central control unit is set in each of the LANtype telephone sets in advance of any call initiated by any of the LANtype telephone sets.
 14. The hybrid telephony system as claimed in claim5, further comprising: the time-division switch provided in the exchangeunit for providing time division data transfer among the conventionaltype telephone sets, wherein the central control unit controls thetime-division switch by way of the control bus, to allow data to be sentto the one of the conventional type telephone sets via the gateway unitand the time-division switch along the communication path establishedbetween the one of the conventional type telephone sets and the gatewaycircuit.
 15. The hybrid telephony system as claimed in claim 1, whereinthe central control unit controls establishment of connections for allcalls made between any two of the LAN type telephone sets, between anytwo of the conventional type telephone sets, and between any one of theLAN type telephone sets and any one of the conventional type telephonesets.
 16. The hybrid telephone system as claimed in claim 1, furthercomprising: a maintenance and management terminal that iscommunicatively connected to the central control unit via the controlbus, wherein the maintenance and management terminal is configured toperform maintenance and management for the hybrid telephony system, sothat the central control unit can set control data and monitor control.17. The hybrid telephony system as claimed in claim 6, furthercomprising: the time-division switch provided in the private exchangeunit for providing time division data transfer among the conventionaltype telephone sets, wherein the central control unit controls thetime-division switch by way of the control bus, to allow data to be sentto the one of the conventional type telephone sets via the gateway unitand the time-division switch along the communication path establishedbetween the one of the conventional type telephone sets and the gatewaycircuit.
 18. The hybrid telephony system as claimed in claim 2, whereinthe central control unit controls establishment of connections for allcalls made between any two of the LAN type telephone sets, between anytwo of the conventional type telephone sets, and between any one of theLAN type telephone sets and any one of the conventional type telephonesets.
 19. The hybrid telephone system as claimed in claim 2, furthercomprising: a maintenance and management terminal that iscommunicatively connected to the central control unit via the controlbus, wherein the maintenance and management terminal is configured toperform maintenance and management for the hybrid telephony system, sothat the central control unit can set control data and monitor control.20. A hybrid type telephony system comprising: a time-division switch inwhich conventional type telephone sets are connected; an IP switch inwhich LAN type telephone sets are connected; a gateway circuit whichperforms converting between a first voice format to connect theconventional type telephone sets and a second voice format to connectthe LAN type telephone sets; a LAN which connects the gateway circuitand the IP switch; a control bus which connects the time-divisionswitch, the IP switch, and the gateway circuit; and a central controlunit, connected to the LAN by way of the control bus, which establishesa communication path of the time-division switch, performs a switchingcontrol of IP packets in the IP switch, and controls the gateway circuitand manages IP address information of the LAN type telephone sets andthe gateway circuit via the LAN, and which controls connection betweenthe LAN type telephone sets and the gateway circuit.
 21. A devicecomprising: a time-division switch configured to process voice calls toand from a first type of telephone set; an Internet Protocol (IP) switchconfigured to process voice calls to and from a second type of telephoneset; a gateway circuit configured to convert signals between the firsttype of telephone set and the second type of telephone set; and acentral control unit connected to the time-division switch, the IPswitch, and the gateway circuit via a control bus and being configuredto manage the time-division switch, the IP switch, and the gatewaycircuit to allow for voice communications between the first type oftelephone set and the second type of telephone set.
 22. The device ofclaim 21 wherein the first type of telephone set includes an analogtelephone and the second type of telephone set includes an LAN-typetelephone set.
 23. The device of claim 21 wherein, when managing, thecentral control unit is configured to: lookup an IP address of adestination second type of telephone set.